can be computed
through the Laplace transform [1]}, i.e.,
\(R_{\lambda } = \frac{1}{{E}_B}\int _0^{+\infty }\,\mathrm {d}s \,\mathrm {e}^{\lambda s}\, \,\mathrm {e}^{- \frac{s}{\epsilon _B}H_B}\, .\) 
